A new titanosaur from the La Colonia Formation (Campanian-Maastrichtian), Chubut Province, Argentina

Abstract

Knowledge of the Campanian-Maastrichtian titanosaurian sauropods from southern South America has increased markedly in recent years. Several taxa have been reported from northern Patagonia, as well as few taxa from southern Patagonia that were described in the last years. However, titanosaurs from the end-Cretaceous of Central Patagonia are poorly known. Here we report the associated remains of a new species of a titanosaurian sauropod from the La Colonia Formation found in northern Chubut Province. Titanomachya gimenezi gen. et sp. nov. is represented by a caudal vertebra and appendicular elements. Titanomachya, is interpreted as a member of Lithostrotia, sharing derived features with saltasaurids and bearing unique characteristics in the astragalus. The astragalus morphology of Titanomachya display an intermediate form between Colossosauria and Saltasauroidea, allowing articulation between zeugopodium and autopodium with contributions from both the tibia and fibula. The type specimen is a small-sized adult,estimated at 5.8–9.8 tons. Comparative analyses reveal distinct sauropod faunas in different Patagonian regions and Brazilian formations during the Campanian – Maastrichtian. In northern Patagonia, aeolosaurines and saltasaurines predominate, while in southern Patagonia predominate colossosaurians and other large titanosaurs. The less well-known sauropod fauna from central Patagonia includes aeolosaurines, eutitanosaurs, and the addition of small-bodied saltasauroids such as Titanomachya.